The overall objectives of this project are to determine the importance of DNA repair to both the development of cancer and cancer therapy. Specifically, we are studying a variety of DNA repair inhibitors to localize their effects with respect to repair pathway inhibited and the specific steps inhibited so that these agents may be used as tools to study the biological significance of DNA repair. Goals for the current year include the use of photoaffinity labeling as a new technique for studying DNA repair as well as the initation of methodology for beginning to localize the specific repair steps with respect to pathway and enzyme involved. BIBLIOGRAPHIC REFERENCE: Nishida, M., Mishima, Y., Kawasa, J. and Yielding, K.L. "Enhancement by Nalidixic Acid of the Thermal Sensitivity of the Ts-7 Mutant of Escherichia coli TAU-Bar" Antimicrobial Agents and Chemotherapy 8: 384 (1975).